In recent years, a nano biosensor for detecting proteins in blood has been a major topic in the research of fusion technologies that combine biotechnologies and nanotechnologies.
This research has led to the proposal of biosensors based on silicon technology that would allow mass production using semiconductor processes. One such biosensor is a silicon nanowire biosensor which uses silicon nanowires to quantitatively detect and analyze specific biomaterials.
The silicon nanowire biosensor senses a change in channel electrical conductivity resulting from binding between a charged target material and a probe molecule fixed on the surface of an electrical channel composed of silicon nanowires. Unlike a fluorescent labeling method commonly employed at present, the silicon nanowire biosensor can simultaneously sense various materials within a sample with high sensitivity, in real time, and without additional biochemical processing of the sample to be measured.
FIG. 1 illustrates a conventional silicon nanowire biosensor.
Referring to FIG. 1, a silicon nanowire channel 106 where current flows is electrically separated from a bottom substrate 102 by an insulating layer 104, and probe molecules 110 are fixed on the surface of the silicon nanowire channel 106.
A sample 114 injected into the biosensor through a fluidic channel 112 may be gaseous or liquid and includes a target material 116 which is specifically bound to the probe molecules 110 already fixed on the surface of the silicon nanowire channel 106, and nonspecific molecules 118 which are not bound to the probe molecule 110.
The binding of the target material 116 within the injected sample 114 to the probe molecules 110 fixed on the surface of the nanowire channel 106 changes the surface potential of the nanowire channel 106, which changes its band structure.
This changes the charge distribution within the nanowire channel 106, which changes the electrical conductivity of the nanowire channel 106.
The change in electrical conductivity can be measured using a specific processor coupled to the nanowire channel through the electrode 108 to thereby detect the target material 116 within the sample 114.
A bottom-up approach such as a vapor-liquid-solid (VLS) growth method was initially employed to fabricate the silicon nanowire. However, it was difficult to align the nanowires at a desired position, and thus such a bottom-up approach was not conducive to device reproducibility and reliability.
In response to this problem, semiconductor microfabrication technology taking a top-down approach, such as lithography and etching, was recently proposed to pattern the nanowire on a silicon-oxide-insulator (SOI) substrate and use the patterned nanowire as a channel to detect a bio material.
However, the line width of the nanowire used as the channel must have a value of several nanometers to several tens of nanometers in order to detect the bio material with high sensitivity. Such a narrow line width requires a nano patterning technology such as electron beam lithography, which is costly and inefficient.